This invention relates to a method and composition for enhancing the desirable effects of drugs comprising indirect-acting sympathomimetic amines.
Indirect-acting sympathomimetic amines function by releasing stored norepinephrine from sympathetic nerve endings. The major problem with their use is that after a few doses, they often stop functioning,i.e., tachyphylaxis sets in. Tachyphyl-axis is known to be associated with partial depletion of the norepinephrine in the nerve endings, leading to the supposition that there are releasable and non-releasable pools of norepinephrine and that when the drugs cease functioning, it is because the releasable pools have been severely depleted.
Prior to the present invention, tyrosine or a tyrosine precursor has been administered concomitantly with a drug in order to enhance the effectiveness of the drug or to reduce or eliminate undesirable effects associated with the drug.
U.S. Pat. No. 4,224,343 discloses the administration of tyrosine or a tyrosine precursor concomitant with a drug which has the undesirable effect of increasing prolactin secretion, thereby to decrease prolactin secretion. Examples of such drugs are reserpine, aldomet and clonidine.
U.S. Pat. No. 4,271,192 discloses that tyrosine can be administered with drugs known to reduce the risk of ventricular fibrilation in order to potentiate the drugs' activity. Representative suitable drugs include procainamide, quinidine, propranolol and diphenylhydantoin.
U.S. Pat. No. 4,327,112 discloses the administration of tyrosine or a tyrosine precursor to a human together with a drug known to increase blood pressure in order to potentiate the dugus activity for increasing blood pressure. Typical drugs disclosed are neosynephrine, calcium chloride, ephedrine, dopamine and dorepinephrine.
U.S. Pat. No. 4,470,987 also disclosed the use of the combination of tyrosine and a drug in order to prevent ventricular fibrilation.
It would be desirable to provide a means for preventing tachyphylaxis with indirect-acting sympathomimetic amine drugs so that the drugs could be rendered useful for long periods.